This invention relates to a temperature-compensated current source for energizing a Hall element in an analog magnetic-field detector, and more particularly to such a current source that produces a Hall-energizing current which changes proportionally with the circuit energizing DC voltage.
It is known to use a current source to energize a Hall element which has been recognized as providing greater stability of Hall element gain (the Hall-output-voltage per unit magnetic-field) with changes in temperature than does the more commonly used DC voltage source for energizing the Hall element. This is understood to be true because the resistivity of the Hall element body typically has a large temperature coefficient whereby with a constant energizing voltage the Hall output voltage produced is always proportional to the resulting Hall energizing current. However, even with a constant current-source energizing current in a Hall element, the Hall output voltage produced in response to a given level of ambient magnetic field is known to vary over temperature by some amount. Thus with constant current excitation, the Hall output voltage is still subject to changes with temperature.
It is an object of this invention to provide a Hall energizing current source capable of compensating for the variations of the Hall output voltage with temperature.
It is a further object of this invention to provide a Hall energizing current source wherein for the situation that the DC supply voltage (Vcc) changes, the Hall energizing current will change proportionally. The Hall element gain will consequently be proportional to the magnitude of the DC supply voltage.
It is a further object of this invention to provide a means of adjusting the Hall energizing current without affecting the temperature coefficient of that same Hall energizing current.